Prior art devices which might be compared to devices of the present invention are relatively unknown. One known device which may be noted, but which is not a good comparison is a jack-screw having a pair of jaw nut members threaded thereon, one of which has internal left hand threads and the other which has internal right hand threads. Rotation of the screw in such known jack-screws will cause the jaw members to axially translate toward and away from each other in a clamping or spreading action. However, as is well-known, such devices have high frictional losses particularly when attempts are made to produce high clamping or spreading forces.